Existing finFET technology uses a nitride capping layer to cap dopants contained in borosilicate glass (BSG) and phosphosilicate glass (PSG) layers deposited over fins. Some finFET technologies use a silicon oxynitride (SiNO) liner(s) over fins. The nitride capping layer is deposited over the BSG and PSG layers with a low pressure chemical vapor deposition (LPCVD) or at atomic layer deposition (ALD) to a thickness of about 2 nanometers (nm). Problems arise during post processing steps including high temperature annealing and/or high temperature deposition during which the nitride capping layer is consumed and oxidized, thereby rendering the capping layer ineffective in keeping the dopants from diffusing out and being lost. Another problem is the dishing or recessing of a thickness of the fins following chemical mechanical polishing (CMP) as a result of a high removal rate due to insufficient densification of the fins.
A need therefore exists for methodology enabling the application of a diffusion barrier film which can endure post processing steps including CMP, high temperature annealing and/or high temperature deposition and prevent dopants from diffusing out from the fins, and the resulting device.